: In article , : says... : > We thought of carrying our own compresser, but a reliable : > power source and the potential of an extension cord giving large : > voltage drops is a real concern. : > : Oh dear. Are you sure you're qualified to work on the electronics : coming out with a daft statement like the above about the extension : cord?
What shall we consider? 13A going through a 100m long extension of
2.5mm^2 cross section?
Resistivity of copper is (FX: flick, flick) 16.8 nohm m, so the resistance is (16.8 x 10^-9) x 100 / (2.5 x 10^-6) which is 0.67 ohm. Per conductor, of course, so that's a voltage drop in each of 13A x
0.67 ohm = 8.73V. Feed it with 240V and the compressor will see 240 - (2 x 8.73) = 222.5V. Since power is proportional to square of voltage, that's a drop of 14% at the compressor.
Ian